Hydraulic circuits



J. FAISANDIER 3,087,307

HYDRAULIC CIRCUITS April 30, 1963 Filed June 5, 1961 2 Sheets-Sheet 1 Aril 30, 1963 J. FAISANDIER 3,087,307

HYDRAULIC CIRCUITS Filed June 5, 1961 2 Sheets-Sheet 2 United StatesPatent Ofiiice dfifiLBfl-T Patented Apr. 30, 1953 3,0875%? HYDRAULECQERCUZTE; Eacques Faisandier, 32 Blvd. Felix Faure,tlhatiilon-sous-Eagneux, France Filled dune 5, 1961, Ser. No. 1i4,97Ciaims priority, application France dune 21, 1366 6 tClai-ms. (Cl.6---9'7) The invention relates to hydraulic circuits, and in particularto high pressure hydraulic circuits with multiple hydraulic jacks.

For certain purposes, it may be desirable not to leave the generalcircuit at high pressure, and in particular not to let the pump supplythe circuit at high pressure, especially when it is used withinterruptions of greater or less duration.

The pro lem has already been solved by the use of decompression valveswhich automatically reduce the pressure in the circuit as soon as noreceiver elements are connected to the circuit and all the distributorelements are in the neutral position.

However, to reestablish anew the high pressure level in the circuitrequires a special operation, generally to obtain momentarydecompression which moves the decompression valve into the operatingposition.

The object of the invention is to render this operation automatic, sothat it will respond to each of the distributors individually. On theone hand, greater simplicity and rapidity of the operation is achieved,and on the other hand the system of pipes is greatly simplified.

With this object in view, the invention comprises a device adjacent tothe control of each distributor so that the latter, which normally havetheir centres closed, momentarily have their centres open.

Below will be given by way of example, an embodiment of the invention,although the general scope of the invention is in no way limited to theparticular features or by the specific features of the example chosen asillustration.

In the attached drawings:

FIGURE 1 is a general plan of the hydraulic circuit of the invention.

FIGURES 2 and 3 are respectively partial views of two differentembodiments; the parts which are similar to those in FIGURE 1 have notbeen shown again.

The described installation may comprise any number of receiver elements1, each of which is controlled by a distributor 2. The distributors areconnected in parallel between the general feed circuit 3 and the generalreturn circuit 4 at the tank 5. For the sake of clarity, only a singlegroup comprising a receiver 1 with distributor 2 has been shown. Theother groups are identical to it or of the same type. The generalcircuit, which is shown open at 6 and '7, is in fact closed by thedistributor or distributors not shown, and all circulation of fluid isinterrupted in the general circuit when all the distributors are set toneutral, by definition even of the distributors with closed centre. Thegeneral circuit is supplied by the pump 8 through the usual non-returnvalve 9. Connected to the high pressure duct 3 of the general circuit isthe decompression valve 16, including a valve distributor the piston 12of which is under the action of the spring 213. The movement of thepiston 12 against the action of the spring 13 is limited, in this caseby the stop 14. The centre of the distributor is closed. The pumppressure acts on the centre through the inlet 15 and the pressure of thegeneral circuit acts at 16 on the piston, at the end opposite to that atwhich the spring 13 acts. An auxi-liary circuit 17 returns fluid to thecistern 5. The three chambers formed by lands of piston 12 are connectedwith 17 through the outlets 18, 19' and 2d. The outlets 18 and 19establish a permanent communication with 17 but 29 is normally closedand opens only when the piston moves to the left. The outlets 19 and 20are limited by a throttle 21 which is shunted by the calibrated valve22..

The distributor 2 comprises a double slide valve having lands 23, 24forming the usual distributor slide valve properly speaking for thereceiver 1, whereas the elements 25, 2s constitute the lands of anauxiliary slide valve the function of which is to connect the centre ofthe first slide valve, which is normally closed, momentarily with thecistern whereby a momentary drop in pressure is caused in the supplycircuit to actuate valve 12. For this purpose, the slide valve assemblyis hollow and forms a closed chamber which is permanently incommunication with the general circuit through the pipe system 37 andthe apertures 2'7 and the median chamber between the elements 28, 24,and with the cistern by means of the pipe system 34 and the apertures28, 29 which are normally closed but are open as soon as the slide valveis slightly displaced from the neutral position and are closed again assoon as this movement increases. The nonoperating chambers of the doubleslide valve are permanently in communication with the cistern throughthe apertures 39, 31, 32, 33 and the system of pipes 34.

The double slide valve assembly is controlled by the lever 35 which ishinged at 38, with a pivot at 39, and the conventional spring notrepresented is provided to return the slide valve into the neutralposition.

If all distributors are out of service their slide valves will be in theneutral position, and there will be no further flow through the circuit3, so that the pressure will rise at 16 and push the piston to the leftagainst the action of the spring 13. For the sake of illustration, itwill be supposed that this pressure is 250 kg./cm.

On moving to the left, the slide valve opens the aperture 2th so thatoil can flow towards 19, which increases the thrust to the left but atthe same time permits flow across the aperture of the throttle 21 andthe calibrated valve 22.

Supposing the combined action out 21 and 22 produce a pressure of 40kg./cm. on the upstream side of 21 and 22 and that the useful crosssection S is 7 times that of S the piston will move to its left stop 14and the whole circuit will be under a pressure of 40' kg/cm at whichthere is no strain on any of the structural elements, even if it ismaintained permanently.

In order to put one of the hydraulic jacks into operation, it isnecessary to raise the pressure of the general circuit 3 again, which iseffected automatically by the invention as soon as one of the hydraulicjacks is actuated in one sense or another by its control 35 that is assoon as one of the apertures 28 or 29 puts the median chamber or" thedistributor 2 into communication with the cistern 5.

At that moment, the pressure in the general circuit will fall from 40kg./cn1. to 25 lag/cm for example the piston of valve 12 will move tothe right under the action of the spring 13, closing 2% and thus cuttingoff the pump from the cistern, and the pressure in 19 will fall. Thepressure may then be raised again to 250 kg/cm. in the general circuitwithout disturbing the equilibrium of the piston of the slide valve 12.The stopping of the double slide valve of the distributor 2 in thepositions with open centre is only momentary. These positions may bemarked by a catch stop to allow the pressure to descend to 25 kg./cm.before the control movement pursues. The control for releasing thecatch, which is not shown, which immobilises the control, may be manual,or automatic by hydraulic means, the releasing movement taking place assoon as the pressure in the general circuit has dropped to 25 kg./cm.

As soon as the slide valve of the distributor 2 has passed the bypassposition, the centre of the distributor is closed again, and thedistributor again operates in the usual manner. The return of the slidevalve of the distributor 2 to the neutral position is ensured bycustomary spring means not shown in the drawing.

Instead of using the distributor 2 shown in FIGURE 1, the momentaryby-pass from the closed centre of the distributor may be realised byother suitable means.

For example, according to the variations shown in FIG- URE 2 and FIGURE3, the usual type of distributor 4% with closed centre may be usedinstead of the distributor 2 in FIGURE 1.

FIGURE 2 shows the distributor 40 the slide valve of which isarticulated at 38 to the lever '35. Between the two pipe systems 37 and34- is disposed a by-pass device, consisting of a three-way valve 41controlled by the linkage system 42 articulated at 43 to the lever 35.The valve .41 is shown in the medium position; movement in one directionor the other from this central position produces an instantaneousby-pass, communication between 34 and 37 being again cut oil? bycontinued movement of 41 in the same direction.

In FIGURE 3, the usual distributor 40 with closed centre has not beenshown again. Only its connection at 38 on the lever 35' has been shown.

The three-way valve 41 in FIGURE 2 is replaced by a three-waydistributor 44, the passage 45 communicating with the pipe system 37 andthe two passages 46, 47 communicating with the return pipes 34 leadingto the cistern. The distributor slide valve 44 is hinged at 43 to thelever 35. It will be seen again that if the lever 35 moves the slidevalve of the distributor to the right or left, it produces a momentaryby-pass between the pipe systems 34 and 37 which ceases when the slidevalve continues to movein the same direction.

Any other equivalent device may be used to replace the elements 41 and44 if they produce the same effect, that is .to say a momentary by-passas soon as the lever 35 which controls the distributor 40 is actuated.

What I claim is:

1. In a hydraulic pressure system comp-rising a delivery circuit, apressuresource and a reservoir, said system including a by-pass valveconnected between the pressure source and the reservoir and incommunication therewith, said by-pass valve being responsive to pressurein the delivery circuit and to bias means, a return circuit, areversible motor connected in series between said delivery circuit andsaid return circuit, a distributor valve in the path of flow of fluidfrom said reversible motor, a valve in said distributor valve having aneutral position in which the path of flow is obstructed and movableselectively to one of two operating positions in which the path of flowis unobstructed, one operating position of said valve in saiddistributor valve being on each side of said neutral position thereof, asupplementary by-pass means to bypass momentarily said distributor valvein response to displacement of the valve of said distributor valve to aposition intermediate said neutral position and one of the operatingpositions whereby a momentary drop of pressure is caused in the deliverycircuit which permits said bias means -.to actuate said first-namedbypass valve and displace the same towards a closed position.

2. A system as set forth in claim 1, in which said distributor valvecomprises a cylinder, a slide valve slidable in said cylinder and havingportions thereof defining internal chambers, said cylinder and saidchambers each having portions defining port means disposed to by-passsaid motor in each of said intermediate positions of said valve.

3. A system as set forth in claim 1, in which said supplementary by-passmeans includes a by-pass valve mounted in parallel relative to saiddistributor valve, said last-named by-pass valve comprising a movablevalve element, and control means common to the valve of the saiddistributor valve and to said valve element.

4. A hydraulic pressure system comprising a pressure source, a deliverycircuit, a return circuit, a reversible motor connected in seriesbetween said delivery circuit and said return circuit, a reservoir, 21by-pass circuit connected between said delivery circuit and saidreservoir and including a first bypass valve, throttle means in saidby-pass circuit to develop a predetermined pressure intermediate themotor operating pressure and the pressure in the reservoir, said by-passvalve being responsive to the pressure in the delivery circuit to openthe by-pass when the pressure in the delivery circuit raises above themotor operating pressure and to close the by-pass when the pressure inthe delivery circuit drops below said intermediate pressure, adistributor valve in the path of flow of fluid for said motor, a valvein said distributor having a neutral position in which the path of flowis obstructed and movable selectively to one of two motor operatingpositions in which the path of flow is unobstructed, a supplementaryby-pass means to by-pass said distributor and said motor, saidsupplementary by-pass means being operatively connected with said valvein said distributor, said supplementary by-pass means being disposed toopen the bypass only when said valve in said distributor is in apredetermined position intermediate said neutral position and one of theoperating positions, whereby a momentary drop of pressure is caused inthe delivery circuit, as long as said valve in said distributor remainsin said intermediate position, to actuate said first by-pass valve.

5. A hydraulic pressure system comprising a pressure source, a deliverycircuit, a return circuit, a plurality of .parallelly connected motorsbetween said delivery circuit and said return circuit, a reservoir, aby-pass circuit connected between said delivery circuit and saidreservoir and including a first by-pass valve, throttle means in saidby-pass circuit to develop a predetermined pressure intermediate theoperating pressure of said motors and the pressure in the reservoir,said by-pass valve being responsive to the pressure in the deliverycircuit to open the bypass when the pressure in the delivery circuitrises above the motors operating pressure and to close the by-pass whenthe pressure in the delivery circuit drops below said intermediatepressure, a distributor valve for each motor in the path of flow offluid for the corresponding motor, a valve in said distributor having aneutral position in which the path of flow is obstructed and movableselectively to one of two operating positions of said motors in whichthe path of flow is unobstructed, a supplementary by-pass for eachdistributor, means to by-pass the corresponding distributor and thecorresponding motor, said supplementary by-pass means being operativelyconnected with said valve in said distributor, said by-pass means beingdisposed to open the by-pass only when said valve in said distributor isin a predetermined position intermediate said neutral position and oneof the operating positions, whereby a momentary drop of pressure iscaused in the delivery circuit, as long as said valve in saiddistributor remains in said intermediate position, to actuate said firstby-pass valve.

6. A hydraulic pressure system comprising a pressure source, a deliverycircuit, a reversible motor connected in series between said deliverycircuit and said return circuit, a reservoir, a by-pass circuitincluding a first by-pass valve and connected between said deliverycircuit and said reservoir, said first by-pass valve including acylinder and a differential pression having two positions, a by-passposition and a motor operating position and including a large face and asmall face, said small face partly defining in said cylinder a chamberpermanently connected to the delivery circuit, said large face partlydefining in said cylinder a chamber connected With the delivery circuitwhen the piston is in the by-pass position, said piston being subjectedto bias means acting on the opposite side relatively to said small face,throttle means in said by-pass circuit to develop a predeterminedpressure intermediate the motor-operating pressure and the pressure insaid reservoir, whereby said piston is displaced towards the by-passposition when the pressure in the delivery circuit rises above the motoroperating pressure, maintained in said operating position by means ofsaid intermediate pressure, and displaced towards the motor operatingposition in response to momentary drop of pressure in said deliverycircuit, a distributor in the path of flow of fluid of said motor, avalve in said distributor having a neutral position in which the path offlow is obstructed and movable selectively to one of two motor operatingpositions, in which the path of flow is unobstructed, one operatingposition of said valve in said distributor valve being on each side ofsaid neutral position thereof, a supplementary by-pass means to by-passmomentarily said distributor and said motor valve in response todisplacement of the valve 6 of said distributor valve to a positionintermediate said neutral position and one of the operating positionswhereby a momentary drop of pressure is caused in said delivery circuitto displace said first by-pass valve towards its motor operatingposition.

References Cited in the file of this patent UNITED STATES PATENTS2,057,087 De Millar Oct. 13, 1936 2,243,364 Trautman May 27, 19412,319,551 Linden et a1. May 18, 1943 2,649,688 Slomer Aug. 25, 1953

1. IN A HYDRAULIC PRESSURE SYSTEM COMPRISING A DELIVERY CIRCUIT, APRESSURE SOURCE AND A RESERVOIR, SAID SYSTEM INCLUDING A BY-PASS VALVECONNECTED BETWEEN THE PRESSURE SOURCE AND THE RESERVOIR AND INCOMMUNICATION THEREWITH, SAID BY-PASS VALVE BEING RESPONSIVE TO PRESSUREIN THE DELIVERY CIRCUIT AND TO BIAS MEANS, A RETURN CIRCUIT, AREVERSIBLE MOTOR CONNECTED IN SERIES BETWEEN SAID DELIVERY CIRCUIT ANDSAID RETURN CIRCUIT, A DISTRIBUTOR VALVE IN THE PATH OF FLOW OF FLUIDFROM SAID REVERSIBLE MOTOR, A VALVE IN SAID DISTRIBUTOR VALVE HAVING ANEUTRAL POSITION IN WHICH THE PATH OF FLOW IS OBSTRUCTED AND MOVABLESELECTIVELY TO ONE OF TWO OPERATING POSITIONS IN WHICH THE LECTIVELY TOONE OF TWO OPERATING POSITIONS IN WHICH THE PATH OF FLOW ISUNOBSTRUCTED, ONE OPERATING POSITION OF SAID VALVE IN SAID DISTRIBUTORVALVE BEING ON EACH SIDE OF SAID NEUTRAL POSITION THEREOF, ASUPPLEMENTARY BY-PASS MEANS TO BY-PASS MONENTARILY SAID DISTRIBUTORVALVE IN RESPONSE TO DISPLACEMENT OF THE VALVE OF SAID DISTRIBUTOR VALVETO A POSITION INTERMEDIATE SAID NEUTRAL POSITION AND ONE OF THEOPERATING POSITIONS WHEREBY A MOMENTARY DROP OF PRESSURE IS CAUSED INTHE DELIVERY CIRCUIT WHICH PERMITS SAID BIAS MEANS TO ACTUATE SAIDFIRST-NAMED BY-PASS VALVE AND DISPLACE THE SAME TOWARDS A CLOSEDPOSITION.